Access terminals, such as cell phones and wireless personal digital assistants (PDAs), are operable to communicate with radio access networks, such as cellular wireless networks. These access terminals and access networks typically communicate with each other over a radio frequency (RF) air interface according to a wireless protocol such as 1× Evolution Data Optimized (1× Ev-DO), perhaps in conformance with one or more industry specifications such as IS-856, Revision 0, IS-856, Revision A, and IS-856, Revision B. Other wireless protocols may be used as well, such as Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), Time Division Multiple Access (TDMA), or some other wireless protocol.
Access networks typically provide services such as voice, text messaging (such as Short Message Service (SMS) messaging), and packet-data communication, among others. Access networks typically include a plurality of base transceiver stations (BTSs), each of which provides one or more coverage areas, such as cells and sectors (i.e., individual areas of a cell that allow the cell to carry more calls). When an access terminal is positioned in one of these coverage areas, it can communicate over the air interface with the BTS, and in turn over a signaling network or a transport network, or both. The signaling network may be a circuit-switched network, a packet-switched network or a combination of both. Similarly, the transport network may be a circuit-switched network, a packet-switched network or a combination of both.
Access terminals and access networks may conduct communication sessions (e.g. voice calls and data sessions) over a pair of frequencies known as carriers, with a BTS of an access network transmitting to an access terminal on one of the frequencies, and the access terminal transmitting to the BTS on the other. This is known as frequency division duplex (FDD). A BTS-to-access-terminal communication link is known as the forward-link, while an access-terminal-to-BTS communication link is known as the reverse-link.
Access terminals may be mobile such that the access terminals can be transported between different coverage areas while the access terminals are operating in an idle mode (e.g., a mode in which the access terminals are not carrying out communication sessions) or an active mode (e.g., a mode in which the access terminals are carrying out communication sessions). A given coverage area provided by an access network may reach a capacity for carrying out communications if too many access terminals are carrying out and/or are trying to carry out communications while in the given coverage area. An access network may be arranged to compensate for coverage areas operating at their capacity.